CVE-2018-16297 in Foxit
Summary
by MITRE
An exploitable use-after-free vulnerability exists in the JavaScript engine of Foxit Reader before 9.3 and PhantomPDF before 9.3, a different vulnerability than CVE-2018-16291, CVE-2018-16292, CVE-2018-16293, CVE-2018-16294, CVE-2018-16295, and CVE-2018-16296. A specially crafted PDF document can trigger a previously freed object in memory to be reused, resulting in arbitrary code execution. An attacker needs to trick the user to open the malicious file to trigger this vulnerability. If the browser plugin extension is enabled, visiting a malicious site can also trigger the vulnerability.
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Analysis
by VulDB Data Team • 07/31/2024
This vulnerability represents a critical use-after-free flaw in the JavaScript engine of Foxit Reader and PhantomPDF products, affecting versions prior to 9.3. The issue stems from improper memory management where a JavaScript object is freed from memory but remains accessible through existing references, creating a scenario where subsequent operations on the freed object can lead to unpredictable behavior. The vulnerability operates through a sophisticated exploitation chain that leverages the PDF processing engine's JavaScript interpreter, specifically targeting memory corruption mechanisms that occur during object lifecycle management. This type of vulnerability falls under the CWE-416 category of Use After Free, which is classified as a serious memory safety issue that can lead to complete system compromise. The attack vector requires user interaction through opening a malicious PDF file, making it particularly dangerous in environments where users frequently open documents from untrusted sources. The vulnerability is distinct from several other related issues in the same product line, indicating a unique code path that was not addressed by previous patches, suggesting either a separate code module or a different exploitation technique.
The technical implementation of this vulnerability involves a race condition or memory management error within the JavaScript engine's garbage collection and object reference tracking mechanisms. When processing specific JavaScript code embedded within malicious PDF documents, the engine fails to properly invalidate object references after memory deallocation, allowing attackers to manipulate the freed memory location. This creates a scenario where an attacker can overwrite the freed object's memory with malicious data and subsequently trigger the object's methods, leading to arbitrary code execution. The exploit requires precise control over memory layout and object placement, making it a sophisticated attack that typically involves multiple stages of exploitation including information leakage, memory spraying, and payload delivery. The vulnerability is particularly concerning because it can be triggered through both file-based and web-based attack vectors, with the browser plugin extension enabling remote exploitation when users visit malicious websites. This dual attack surface significantly increases the potential impact and attack surface for exploitation.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass full system compromise and potential data exfiltration. Successful exploitation allows attackers to execute arbitrary code with the privileges of the affected application, typically the user's context within the PDF reader environment. This can lead to persistent backdoor installation, credential theft, and lateral movement within the network. The vulnerability's presence in both desktop and web-based PDF processing environments means that organizations must consider multiple attack vectors and user interaction points. The fact that this vulnerability affects PDF processing engines used in enterprise environments makes it particularly dangerous as it can be leveraged for targeted attacks against high-value targets. Security teams must understand that exploitation of this vulnerability can occur through social engineering campaigns targeting document opening behavior, making user awareness and security training crucial components of defense. The vulnerability also demonstrates the inherent risks of complex JavaScript engines in document processing applications, where the interaction between multiple subsystems can create unexpected attack surfaces.
Mitigation strategies for this vulnerability must address both the immediate patching requirements and broader security posture improvements. Organizations should prioritize immediate deployment of patches from Foxit and PhantomPDF vendors to upgrade to versions 9.3 or later where the vulnerability has been addressed. Network-based mitigations including PDF file filtering and sandboxing mechanisms can provide additional protection layers, particularly for environments where immediate patching is not feasible. The implementation of strict access controls and user behavior monitoring can help detect potential exploitation attempts by monitoring for unusual document processing patterns or attempts to access freed memory locations. Security teams should also consider implementing browser security extensions and content filtering solutions to prevent access to known malicious websites that may host exploit code. Regular security assessments of PDF processing environments and JavaScript engine configurations are essential to identify potential additional vulnerabilities. The vulnerability serves as a reminder of the importance of maintaining up-to-date security patches and implementing defense-in-depth strategies, as the use-after-free nature of the flaw makes it particularly difficult to detect and prevent through traditional security measures. Organizations should also consider implementing application whitelisting policies and restricting the execution of untrusted PDF documents in sensitive environments.